Grinding machine

ABSTRACT

A grinding machine ( 3 ) for grinding drill bits ( 6 ), having a grinding unit ( 9 ) which includes a motor unit ( 10 ) and a spindle ( 11 ) which is driven by the motor and which carries a grinding wheel ( 12 ) for rotation by the spindle ( 11 ) and for grinding a button bit ( 8 ) in the drill bit ( 6 ), wherein the grinding unit ( 9 ) together with the grinding wheel ( 12 ) is adapted to swing forwards and backwards about a vertical shaft which coincides generally with the geometric axis of the button bit ( 8 ).

The present invention relates to a grinding machine, and morespecifically to a back-carried grinding machine for grinding or honingdrill bits.

Drill bits are subjected to a great deal of wear and must be well-honedin order to drill rock effectively. Bits that are poorly sharpened donot only impair the efficacy of rock drilling, but also cause the drillstring and the drilling rig to be subjected to a great deal of stressand strain and also wear.

Consequently, there is a great need for grinding, honing, drill bits atregular intervals. There exist to this end special semi-automaticgrinding machines for grinding the button bits and also for grindingdown the steel included in the drill bit, at the same time.Transportable grinding machines that enable the button bit to be groundat the site where drilling takes place are also available commercially.These machines may be semi-automatic machines or manually operatedmachines and are exclusively of the type that use grinding cups.

Accordingly, an object of the present invention is to provide a grindingmachine of the aforesaid kind which can function at leastsemi-automatically and which can be used to recreate both a sphericaland ballistic button bit and which can be mounted on a drilling rig oron a separate readily transportable arrangement.

This object is achieved with a button bit grinding machine comprising agrinding unit that includes a motor unit which drives a spindle to whicha grinding wheel is fitted for rotation by said spindle and therewithsharpen or hone a button bit in the drill bit crown. According to theinvention, the grinding unit together with the grinding wheel areadapted to be swung forwards and backwards about a vertical shaft thatcoincides generally with the geometric axis of the button bit.

The invention will now be described in more detail with reference to anon-limiting exemplifying embodiment thereof and also with reference tothe accompanying drawings, in which

FIG. 1 is a side view showing the grinding machine in an adjustedsetting in which the grinding wheel is centred around a button bit on adrill bit crown;

FIG. 2 illustrates a grinding unit in a grinding intermediate position,although said unit is shown distanced from the drill bit crown for thesake of clarity;

FIG. 3 illustrates the grinding unit in a first turning position,although corresponding to the view of FIG. 2 in other respects; and

FIG. 4 illustrates the grinding unit in a second turning position.

The grinding machine illustrated in the accompanying drawings isintended to be mounted on a drilling rig and includes a carrier frame 1intended for fastening to a drilling rig, not shown. The frame 1 has anupper, outwardly projecting carrier arm 2 which carries the grindingarrangement 3 of said grinding machine via a bracket structure 4 thatcan be displaced in the horizontal plane. The grinding arrangement 3 canbe raised and lowered in the bracket structure 4, i.e. can be displacedin the vertical plane. The frame 1 also includes a holder arm 5 which islocated beneath the grinding arrangement and adapted to hold firmly adrill bit crown 6. The drill bit crown 6 can be readily fitted to andlocked in the holder arm 5, with the aid of a locking lever 7. The crown6 includes a number of button bits 8. The number of button bits 8included, and their size and placement on the crown 6, may vary. Thecrown may also be locked obliquely in the holder arm 5, to enablecorrect grinding of the peripheral button bits 8 a in the drill bitcrown 6.

The grinding arrangement 3 includes a grinding unit 9 which, in turn,includes a motor 10, a spindle 11 and a grinding wheel 12 carried on theend of the spindle 11. The grinding unit 9 is fitted so that the spindlewill slope slightly in relation to the horizontal plane, wherein thegrinding wheel 12 rotates about said spindle. The grinding wheel 12 isof a known type and is provided with a diamond coating and may bedesigned for grinding spherical or ballistic button bits. The grindingunit 9 is carried by an arm 13 on the grinding arrangement and can beswung about a generally vertical shaft 14 with the aid of a pivotcylinder 15 which is adapted to swing the grinding unit 9 forwards andbackwards between the positions shown in FIGS. 3 and 4, i.e. with apendulum movement of about 180°, preferably slightly greater than 180°.The shaft 14 is arranged so that an extension of the shaft will passthrough the centre of the grinding wheel 12 and so that as the grindingunit 9 swings forwards and backwards, the grinding wheel will move abouta point which corresponds to the top of one of the button bits 8 whenthe grinding arrangement 3 is correctly adjusted. The geometric axisabout which the grinding unit 9 moves forwards and backwards is agenerally vertical axis which coincides with the geometric centre axisof the button bit 8 when the grinding arrangement 3 has been correctlyadjusted in relation to the button bit 8. The grinding unit 9 thus movesforwards and backwards in a pendulum movement in the horizontal plane,so as to be able to grind or hone a button bit 8 that extends generallyvertically on the grinding occasion concerned.

Adjustment to the setting of the grinding arrangement 3 is achieved withthe aid of a centring body 16 which can be placed and centred over abutton bit 8, as shown in FIG. 1. In this position, the centring body islocated in the extension of the shaft 14 and on the geometric axis aboutwhich the grinding unit 9 is intended to swing. When the grindingarrangement 3 has been centred over a button bit in this way, thearrangement 3 is locked against movement in the horizontal plane and canthen be solely raised and lowered. Subsequent to being centred, thegrinding arrangement 3 must first be raised so that the centring body 16can be swung to one side, to the position shown in FIGS. 2-4, and sothat the grinding disc can be lowered down onto the drill bit crown 6and against the button bit 8 for grinding said bit. Locking of thegrinding arrangement in the horizontal plane is the subject of aseparate patent application filed at the same time as the instantapplication.

The grinding arrangement 3 includes an operating lever 17 with whichsaid arrangement can be moved to the correct position in the horizontalplane for adjusting the setting of the arrangement with the aid of thecentring cup 16. The arrangement 3 may also include in connection withthe lever 17 a control device 18 with which movement of said arrangement3 in the horizontal plane can be locked/released. The lever is also usedfor raising and lowering the grinding arrangement. There may also beprovided in connection with the lever 17 activating means with which thegrinding arrangement 3 can be activated, i.e. with which the motor 10can be activated for rotation of the grinding wheel 12, and alsoactivation of the pivot cylinder 15 for causing pendulum movement of thegrinding unit 9. This activation may also take place automatically whenthe arrangement 3 has been brought to its correct position.

The grinding unit 9 is thus able to achieve automatic grinding of thebutton bits 8 in a drill bit crown 6, subsequent to the grinding unit 9having been adjusted manually by the operator in relation to the bit tobe ground. The cylinder 15 is adapted to pivot the grinding unit 9forwards and backwards about the centre of the button bit 8 concerned,for instance for a pre-set period of the time normally taken to grind orhone a button bit. The pendulum movement of the grinding unit willpreferably cover at least 180°, preferably slightly more than 180°, inorder for the bit to be ground correctly.

The grinding wheels 12 used in the grinding machine according to theinvention are of the same type as those used in the grinding machinesmentioned in the introduction for workshop use, and comprisediamond-coated grinding wheels that are available in both spherical andballistic designs, said grinding wheels being chosen in accordance withthe type of button bit to be ground. These wheels have the form of apulley or roller that includes two ends which have a larger diameterthan the intermediate part and which have a spherical or ballisticrecess to give the button bit to be ground the desired shape.

The inventive grinding machine is, as before mentioned, suitably mountedon a drilling rig and is suitably supplied with power, electrical,pneumatic or hydraulic power, and water from the drilling rig.Alternatively, the grinding machine may, of course, be mounted on an owntransportable device, for instance a wagon or carriage, although thiswill then require an additional electrical, pneumatic or hydraulicsupply means for driving the grinding machine. The inventive grindingmachine may also, of course, be used conveniently in a permanentstructure in a workshop environment.

1-9. (canceled)
 10. A grinding machine (3) for grinding drill bits (6), comprising a grinding unit (9) which includes a motor unit (10) and a spindle (11) which is driven by said motor and which carries a grinding wheel (12) for rotation by the spindle (11) and for grinding a button bit (8) in the drill bit (6), characterised in that the grinding unit (9) together with the grinding wheel (12) is adapted to swing forwards and backwards covering an angle of about 180° about a vertical shaft which coincides generally with the geometric axis of the button bit (8).
 11. A grinding machine according to claim 10, characterised in that that the grinding unit (9) is adapted to swing forwards and backwards in a plane close to the horizontal plane.
 12. A grinding machine according to claim 10, characterised in that the grinding unit (9) can be moved in the horizontal plane so as to enable said unit to be centred over a button bit (8) in a drill bit (6).
 13. A grinding machine according to claim 12, characterised in that the grinding machine includes a centring cup (16) for centring the grinding unit (9) over the button bit (8) in said drill bit.
 14. A grinding machine according to claim 13, characterised in that subsequent to centring of the grinding unit (9), said unit can be locked in the horizontal plane so as to be moveable solely in the vertical plane.
 15. A grinding machine according to claim 10, characterized in that the grinding machine is mounted on a drilling rig.
 16. A grinding machine according to claim 10, characterised in that the grinding machine is mounted for transportation on a wagon or carriage.
 17. A grinding machine according to claim 10, characterised in that the grinding machine is fixedly mounted in a workshop environment.
 18. A grinding machine according to claim 11, characterised in the grinding unit (9) can be moved in the horizontal plane so as to enable said unit to be centred over a button bit (8) in a drill bit (6). 